Isothermal compression based combustion engine

ABSTRACT

Systems and methods are disclosed that include operating an isothermal compression based combustion (IsoC) engine by injecting isothermally compressed air into a combustion engine immediately prior to a combustion event in order to increase the efficiency of the engine, improve emissions, and substantially eliminate autoignition and associated design constraints. The IsoC engine utilizes an intercooled compressor to isothermally compress air that is stored in a plurality of capacitance tanks prior to delivery of the compressed air to the combustion engine. The IsoC engine allows combustion to be selectively terminated to increase fuel efficiency, thereby resulting in a hybrid compressed air-motor and internal combustion operated IsoC engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/906,467 filed on Nov. 20, 2013 byDortch, entitled “Isothermal Compression Based Combustion Engine” andU.S. Provisional Patent Application No. 61/935,025 filed on Feb. 3, 2014by Dortch, entitled “Isothermal Compression Based Combustion Engine,”the disclosures of which are hereby incorporated by reference in theirentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Traditional combustion engines include an intake stroke followed by acompression stroke. Generally, a mixture of air and fuel is introducedinto a combustion chamber of the engine during the intake stroke andthereafter compressed by a piston during the compression stroke.Compression of the air/fuel mixture significantly increases thetemperature and pressure of the mixture. Autoignition may occur when thecompressed air/fuel mixture reaches a temperature that causes it tospontaneously ignite prior to a spark plug firing to ignite the air/fuelmixture and may cause damage to the engine. Accordingly, design featuresof traditional combustion engines such as static compression ratio,forced induction capacity, power density, fuel economy, and fuelingoptions are constrained by the limits of autoignition.

SUMMARY

In some embodiments of the disclosure, an isothermal compression basedcombustion (IsoC) engine is disclosed as comprising: a compressorconfigured to isothermally compress a volume of air; at least onecapacitance tank coupled to the compressor and configured to store thevolume of isothermally compressed air; and a combustion engineconfigured to receive at least a portion of the volume of isothermallycompressed air into a cylinder of the combustion engine; at least one of(1) selectively inject a volume of fuel into the cylinder and ignite thevolume of fuel in the presence of the volume of air in the cylinder and(2) selectively omit the injection of a volume of fuel and expand thevolume of air in the cylinder using no combustion.

In other embodiments of the disclosure, a method of operating anisothermal compression based combustion (IsoC) engine is disclosed ascomprising: isothermally compressing a first volume of air; passing theisothermally compressed volume of air to at least one capacitance tank;storing the isothermally compressed volume of air in the at least onecapacitance tank; injecting a second volume of isothermally compressedair into a cylinder of a combustion engine when an associated piston isat about a top dead center (TDC) position; selectively injecting avolume of fuel into the cylinder of the combustion engine; andcombusting the mixture of the second volume of isothermally compressedair and the volume of fuel in the cylinder of the combustion engine.

In yet other embodiments of the disclosure, a method of controlling anisothermal compression based combustion (IsoC) engine is disclosed ascomprising: selectively injecting a volume of isothermally compressedair into a cylinder of a combustion engine when an associated piston isat about a top dead center (TDC) position; selectively injecting avolume of fuel into the cylinder; selectively receiving an input througha user interface; and selectively adjusting at least one of the volumeof compressed air and the volume of fuel injected into a cylinder of thecombustion engine during subsequent rotations of a crankshaft of thecombustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and theadvantages thereof, reference is now made to the following briefdescription, taken in connection with the accompanying drawings anddetailed description, wherein like reference numerals represent likeparts:

FIG. 1 is a schematic diagram of an isothermal compression basedcombustion (IsoC) engine according to an embodiment of the disclosure;

FIG. 2 is a schematic diagram of an isothermal compression basedcombustion engine (IsoC) electronic control system according to anembodiment of the disclosure;

FIG. 3 is a flowchart of a method of operating an isothermal compressionbased combustion engine (IsoC) according to an embodiment of thedisclosure; and

FIG. 4 is a flowchart of a method of controlling an isothermalcompression based engine (IsoC) according to an embodiment of thedisclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

Disclosed herein are embodiments of an isothermal compression basedcombustion (IsoC) engine. The IsoC engine may inject ambient temperaturecompressed air into a combustion engine immediately prior to acombustion event in order to increase the efficiency of the engine. TheIsoC engine may also comprise a turbocharger coupled to an isothermalcompressor and the exhaust stream from the combustion engine to increaseairflow into the compressor. The IsoC engine may further comprisecapacitance air tanks that may be employed to drive the combustionengine pistons and allow combustion to be selectively terminated toincrease fuel efficiency and curtail emissions. The IsoC engine may alsobe compatible with regenerative braking. The IsoC engine may also employlean burns (e.g. combustion of mixtures with an excess of air to fuel inthe combustion chamber) to increase fuel efficiency and decrease exhaustemissions. The IsoC engine may also comprise a carbon sequestrationfilter to further decrease net carbon emissions. Additionally, thecomponents supporting IsoC engine efficiency may provide the hardwarenecessary to operate the engine as a dual-drive hybrid platform. Thehigh pressure pneumatic components of the IsoC engine that facilitatethermal efficiency may also allow the engine to operate as azero-emissions air motor using no combustion at all.

Referring now to FIG. 1, an isothermal compression based combustion(IsoC) engine 100 is shown according to an embodiment of the disclosure.The IsoC engine 100 is a combustion engine that continuously substitutesan isothermally-cooled compression charge (the charge being at, or verynear ambient temperature) for the hot adiabatic compression leveraged intraditional combustion engine cycles. The absence of compression heatinside the IsoC engine 100 cylinders 156 prior to spark-ignitionsubstantially eliminates autoignition as a design boundary for theisothermally compressed combustion engine. Most generally, the IsoCengine 100 comprises an intercooled, multistage compressor 102configured to collect and compress ambient air while rejecting the heatof compression, at least one capacitance tank 104 configured to storethe cooled compressed air, and a combustion engine 106 configured topower a drive drain or other apparatus as a result of injectingisothermally compressed air from the at least one capacitance tank 104and/or fuel supplied by the fuel system 140 into a plurality ofcylinders 156 of the combustion engine 106. Additionally, in someembodiments, the IsoC engine 100 may also comprise a turbocharger 108configured to increase the flow of air to the compressor 102.

The compressor 102 may generally be configured to isothermally compressair and pass the compressed air to at least one capacitance tank 104coupled to the compressor 102. The compressor 102 is generallyconfigured as an intercooled, multistage piston compressor. In someembodiments, the compressor 102 may be a scroll-type compressor. Inother embodiments, the compressor 102 may be a rotary-type compressor.However, in yet other embodiments, the compressor 102 may be any othertype of suitable compressor capable of increasing the pressure of a bodyof air received by the compressor 102. The compressor 102 comprises atleast one compressor fan 138 and at least one heat exchanger 158configured to dissipate heat caused by compressing the air within thecompressor 102. The compressor fan 138 is configured to generate apassing airflow across the heat exchanger 158 to facilitate heattransfer between the passing airflow and the heat exchanger 158.Additionally, the heat exchanger 158 may include fins, heat sinks,intercoolers, and/or any combination of fins, heat sinks, intercoolers,and other features that are configured to promote heat transfer betweena passing airflow and the heat exchanger 158. In some embodiments, heatrejected from the heat exchanger 158 of the compressor 102 may bepurposed to provide cabin heating, oil heating in cold climates, and/orother ancillary uses. The heat exchanger 158 of the compressor 102 mayalso be configured for liquid cooling. By rejecting heat caused by thecompression of air within the compressor 102, the compressor 102 iscapable of isothermally compressing the air within the compressor 102.In some embodiments, the isothermally compressed air may have atemperature that is substantially similar to the temperature of theambient air entering the compressor 102. The passing airflow maydissipate the heat into ambient air or alternatively be diverted througha compressor exhaust 132. The compressor exhaust 132 may be coupled to ahot side 108 b of the turbocharger 108. As will be discussed later infurther detail, by passing the heat rejected from the heat exchanger 158of the compressor 102 through the hot side 108 b of the turbocharger108, heat energy rejected by the heat exchanger 158 of the compressor102 may be recovered by the turbocharger 108 to further increase theefficiency of the compressor 102 and/or the IsoC engine 100.

The compressor 102 supplies isothermally compressed air to the at leastone capacitance tank 104 through a line dryer 112 disposed between thecompressor 102 and the at least one capacitance tank 104. The line dryer112 is configured to remove moisture from the isothermally compressedair coming from the compressor 102. A check valve 114 may also bedisposed between the compressor 102 and the at least one capacitancetank 104. The check valve is configured to prevent isothermallycompressed air from a downstream side closer to the at least onecapacitance tank 104 from flowing in an upstream direction towards thecompressor 102. Additionally, an external fill port 116 may be disposedbetween the check valve 114 and the at least one capacitance tank 104.The external fill port 116 is configured to couple to an externalcompressed air source to allow the at least one capacitance tank 104 toreceive compressed air through the external fill port 116 from theexternal compressed air source. Further, the check valve 114 may alsoprevent compressed air received from an external compressed air sourcethrough the external fill port 116 to flow towards the compressor 102.

While the IsoC engine 100 is disclosed as having at least onecapacitance tank 104, it will be appreciated that the IsoC engine 100may include a plurality of capacitance tanks 104. The capacitance tanks104 are generally configured to store isothermally compressed airreceived from the compressor 102. Further, the capacitance tanks 104 areconfigured to supply a charge of isothermally compressed air to thecombustion engine 106. The capacitance tanks 104 may generally comprisea lightweight, high-strength construction. In some embodiments, thecapacitance tanks 104 may comprise a carbon fiber compositeconstruction. In some embodiments, the capacitance tanks 104 may becharged to a pressure of up to about 500 pounds per square inch (psi),up to about 1,000 psi, up to about 2,000 psi, up to about 3,000 psi, upto about 4,000 psi, and/or up to about 5,000 psi.

On the downstream side of the capacitance tanks 104, the IsoC engine 100includes a shutoff valve 118. The shutoff valve 118 is selectivelyoperable to substantially restrict and/or substantially preventcompressed air stored in the capacitance tanks 104 from passing into thecombustion engine 106. In some embodiments, the shutoff valve 118 may bea manually-controlled shutoff valve. However, in other embodiments, theshutoff valve 118 may be an electronically-controlled valve that may beselectively operated to allow or restrict the flow of compressed airfrom the capacitance tanks 104 to the combustion engine 106. In yetother embodiments, the shutoff valve 118 may be pneumatically actuatedby a sudden change in pressure as a fail-safe emergency cutoff.Additionally, as will be discussed in further detail herein, the IsoCengine 100 may also include a carbon dioxide sequestration filter 120between the capacitance tanks 104 and the combustion engine 106. Thecarbon dioxide sequestration filter 120 may generally comprise acartridge of granulated metal oxides that may sequester free atmosphericcarbon dioxide as the associated IsoC engine 100 is operating.

Most generally, the capacitance tanks 104 are configured to supplycharges of isothermally compressed air into the cylinders 156 of thecombustion engine 106. The capacitance tanks 104 supply the compressedair through a pressure regulator 122 and to a common air rail 124, wherethe compressed air is substantially evenly distributed to a plurality ofair injectors 126. The pressure regulator 122 may generally beconfigured to selectively control, limit, and/or restrict the pressureof the compressed air entering the common air rail and/or the cylinders156 of the combustion engine 106. However, in some embodiments, thepressure regulator 122 may be configured to selectively allow asubstantially unrestricted flow of compressed air to the common air rail124, and/or vary the pressure as a type of throttle in some operatingmodes and conditions. Generally, each cylinder 156 receives compressedair through a single air injector 126. However, in some embodiments,each cylinder 156 of the combustion engine 106 may receive compressedair through a plurality of air injectors 126. The air injectors 126 ofthe IsoC engine 100 may be actuated mechanically, pneumatically,hydraulically and/or electromagnetically. It will be appreciated thatthe delivery of the compressed air from the capacitance tanks 104 to theair injectors 126 and into the cylinders 156 of the combustion enginemay be electronically controlled.

The IsoC engine 100 also comprises a fuel system 140 that is configuredto supply fuel to each of the plurality of cylinders 156 of thecombustion engine 106. The fuel system 140 comprises a fuel reservoir142 configured to store a volume of fuel, a fuel pump 144 configured topump fuel from the fuel reservoir 142, a fuel filter 146 configured toremove particulates from the fuel, a fuel rail 148, and a plurality offuel injectors 150. The fuel system 140 is configured to store a volumeof fuel in the fuel reservoir 142 and pump fuel from the fuel reservoir142 through the fuel filter 146 to the fuel rail 148, where the fuel issubstantially evenly distributed to the plurality of fuel injectors 150.In some embodiments, the fuel system 140 is configured to deliver fuelto the cylinders 156 of the combustion engine 106 simultaneously withisothermally compressed air from the capacitance tanks 104. However, insome embodiments and modes of operation, only compressed air may beinjected into the cylinders 156 of the combustion engine 106.Furthermore, it will be appreciated that the delivery of the fuelthrough the fuel system 140 may be electronically controlled.

The combustion engine 106 is generally configured to operate in responseto combusting a mixture of compressed air delivered from the capacitancetanks 104 and fuel delivered from the fuel system 140. In someembodiments, the combustion engine 106 may also be configured to operatein response to only injecting compressed air from the capacitance tanks104 into the cylinders 156 of the combustion engine 106. In someembodiments, the combustion engine 106 may comprise a four-strokecombustion engine. However, in other embodiments, the combustion engine106 may comprise a two-stroke combustion engine. The combustion enginegenerally comprises a plurality of cylinders 156, each cylinder having apiston 160 that is driven by a crankshaft 136. The combustion engine 106is further configured to expel exhaust gases through an exhaust manifold128. The combustion engine 106 is generally coupled to the compressor102 by a crankshaft 136 through a selectively engaged compressor clutch130. Accordingly, the compressor 102 is selectively driven by thecombustion engine 106 through selective engagement of the compressorclutch 130. By engaging the compressor clutch 130, the rotation of thecrankshaft 136 caused by operating the combustion engine 106 drives thecompressor 102. In some embodiments, the compressor clutch 130 maycomprise additional design and safety elements such as gearing,slip-clutching, and governing the speed and torque delivered from thecombustion engine 106 to the compressor 102. Further, in someembodiments, the compressor clutch 130 may be selectively disengagedwhen the IsoC engine 100 is operating as a compressed air motor.

In some embodiments, the IsoC engine 100 comprises a turbocharger 108.The turbocharger 108 is coupled to the exhaust manifold 128 andconfigured to recover energy from exhaust gases that may otherwise belost. The turbocharger 128 may be described as having a cold side 108 aand a hot side 108 b. The hot side 108 b of the turbocharger 108receives exhaust gases from the combustion engine 106 through theexhaust manifold 128 and passes the exhaust gases through an exhaustpipe 152 to the atmosphere. In some embodiments, depending on theapplication of the IsoC engine 100, the turbocharger 108 may also passthe exhaust gases through a catalytic converter 154. The exhaust gasespassing through the hot side 108 b of the turbocharger 108 rotate ashaft in the turbocharger 108 and cause a second impeller compressor onthe cold side 108 a of the turbocharger 108 to draw ambient air throughthe air filter 110 and force the air into the compressor 102 through anintake pipe 134. The turbocharger 108, when configured to force-inducethe compressor 102, acts as an additional pumping stage, thus improvingvolumetric delivery while reducing the work demand at the compressor 102and/or a crankshaft 136 of the compressor 102. The output of theturbocharger 108 may also be intercooled prior to passing air into thecompressor 102. Additionally, in some embodiments, heat rejected fromthe compressor 102 by the heat exchanger 158 may be diverted to the hotside 108 b of the turbocharger 108 and may be recovered by theturbocharger 108 to further increase the efficiency of the compressor102 and/or the IsoC engine 100. Accordingly, the turbocharger 108 mayincrease the volumetric delivery of the compressor 102 utilizing energyrecovered from the exhaust of the combustion engine 106 and/or heatrejected at the compressor 102. In alternative embodiments, however, theIsoC engine 100 may not include a turbocharger 108. In such embodimentswithout a turbocharger 108, the compressor 102 may be directly coupledto the air filter 110 and configured to draw air directly through theair filter 110 via natural aspiration.

Still referring to FIG. 1, in operation, the IsoC engine 100 is operatedby injecting a charge of isothermally compressed air into a cylinder 156of the combustion engine 106 and injecting fuel supplied by the fuelsystem 140. The charge of compressed air and the fuel may then atomizeand/or mix and be combusted to turn the crankshaft 136 of the combustionengine 106. In some embodiments, the charge of compressed air may beinjected simultaneously with the fuel injection. However, in otherembodiments, the charge of compressed air may be injected prior to thefuel injection and/or after the fuel injection. Additionally, the IsoCengine 100 is configured to selectively cease fuel injection and operateas a zero-emissions compressed air motor by injecting the charge ofcompressed air to force the piston 160 in the associated cylinder 156down away from a top dead center (TDC) position. The IsoC engine 100 isalso configured to selectively resume fuel injection and operate thecombustion engine 106 by resuming combustion of the compressed air andfuel mixture.

Most generally, the charge of isothermally compressed air from thecapacitance tanks 104 may be injected into a cylinder when theassociated piston 160 is positioned at or near the TDC position. TDCrefers to when a piston 160 within a cylinder 156 is located farthestfrom the crankshaft 136. TDC also refers to when the force upon thecrankshaft 136 is substantially aligned with a longitudinal axis thatextends through the center of the cylinder 156. Still further, forpurposes of this disclosure, a piston 160 is positioned at TDC when theassociated crankshaft 136 angle is at 0 degrees. Thus, any negativeangle such as −5 degrees refers to the angle of rotation of thecrankshaft 136 prior to a piston 160 reaching its TDC within anassociated cylinder 156, and any positive angle such as +5 degreesrefers to the angle of rotation of the crankshaft 136 after the piston160 has passed its TDC within an associated cylinder 156. Additionally,it will be appreciated that the IsoC engine 100 may be configured as atwo-stroke combustion engine or alternatively as a four-strokecombustion engine, wherein fuel from the fuel system 140 is alsoinjected into cylinders 156 of the combustion engine 106.

Two-Cycle IsoC Engine Operation

Operation of the IsoC engine 100 when the combustion engine 106comprises a two-stroke combustion engine includes a power stroke and anexhaust stroke and may be further characterized by the omission of aconventional intake stroke and the omission of a conventional adiabaticcompression stroke within the cylinders 156 of the combustion engine106. Instead, a charge of isothermally compressed air from thecapacitance tanks 104 is injected into a cylinder 156 of the combustionengine 106 when the piston 160 of an associated cylinder 156 is at ornear TDC. Additionally, the charge of isothermally compressed air fromthe capacitance tanks 104 may also be described as being injected justprior to ignition when fuel from the fuel system 140 is also added intothe cylinder 156.

In some embodiments, the injection of compressed air into a cylinder 156may occur when the piston 160 of a cylinder 156 is at TDC (0 degrees).However, in other embodiments, the injection of compressed air into acylinder 156 may occur when the angle of rotation of the crankshaft 136is between about −30 degrees to about +30 degrees, about −20 degrees toabout +20 degrees, about −15 degrees to about +15 degrees, about −10degrees to about +10 degrees, about −5 degrees to about +5 degrees,about −2 degrees to about +2 degrees, and/or about −1 degrees to about+1 degrees. In yet other embodiments, the injection of compressed airinto a cylinder 156 may begin when the associated piston 160 ispositioned at TDC and continue until the angle of rotation of thecrankshaft 136 is about +1 degrees, about +2 degrees, about +3 degrees,about +5 degrees, about +10 degrees, at about +15 degrees, and/or about+30 degrees. Still further, in alternative embodiments, the injection ofcompressed air into a cylinder 156 may begin when the angle of rotationof the crankshaft 136 is between about −30 degrees, about −15 degrees,about −10 degrees, about −5 degrees, about −3 degrees, about −2 degrees,and/or about 0 degrees and continue until the angle of rotation of thecrankshaft 136 is about TDC, about +1 degrees, about +2 degrees, about+3 degrees, about +5 degrees, about +10 degrees, about +15 degrees,and/or about +30 degrees. In some embodiments, it will be appreciatedthat the timing and duration of the injection of the compressed air mayfurther be dependent on crankshaft 136 rotational speed and/or otheroperating or design parameters of the combustion engine 106.

The two-stroke combustion engine configuration of the IsoC engine 100eliminates the hot adiabatic compression leveraged in traditionalcombustion engine cycles. By injecting a charge of isothermallycompressed air at or near the TDC position, adiabatic compression heatis not introduced into the cycle and the compressed air-fuel mixtureremains cool to the threshold of spark ignition. Consequently, thetwo-stroke IsoC engine 100 has substantially no autoignition ordetonation constraints, allowing designs and embodiments that mayinclude higher static compression ratios of up to about 100:1, greaterflexibility in fueling choices, improved thermal efficiency, loweredemissions, and the capacity to operate efficiently on very lean air-fuelmixtures. Accordingly, an IsoC engine 100 may combust lean mixtures(e.g. combustion of mixtures of compressed air and fuel with a highratio of air to fuel in the cylinder 156), which may increase fuelefficiency and lower exhaust emissions without causing overheating or asignificant loss of power. In some embodiments, the air-to-fuel ratiomay be about 15:1, about 20:1, about 25:1, about 30:1, about 40:1, about50:1, about 60:1, and/or about 70:1. In some embodiments, the IsoCengine 100 may obtain an equivalent and/or greater amount of power fromcombusting a lean air-to-fuel ratio mixture as a traditional adiabaticcompression engine would obtain combusting a stoichiometric air-to-fuelmixture. Accordingly, the IsoC engine 100 may allow for greater poweroutput with a lower fuel requirement, thereby giving the IsoC engine 100a higher fuel efficiency than the fuel efficiency of a traditionaladiabatic compression engine.

By enabling a combustion engine 106 to operate with air-to-fuel ratiosthat would otherwise damage traditional adiabatic compression engines,longstanding internal combustion engine design constraints may beeffectively reduced and/or altogether eliminated. Additionally, highercompression pressures required for higher compression ratio operationare created and supplied by the pneumatic components of IsoC engine 100,eliminating the requirement that compression forces be handled withinthe combustion engine 106. Consequently, an IsoC engine 100 may comprisea combustion engine 106 of a much lighter duty construction than atraditional combustion engine having a substantially similar staticcompression ratio.

Four-Cycle IsoC Engine Operation

Operation of the IsoC engine 100 when the combustion engine 106comprises a four-stroke combustion engine includes an air motor powerstroke, a compression stroke, a combustion power stroke, and an exhauststroke and may be further characterized by the substitution of the airmotor power stroke for a conventional intake stroke within thefour-stroke cycle. Alternatively, operation of the IsoC engine 100 in afour-stroke configuration may be further described as a four-strokecycle composed of two interlaced and alternating two-stroke cycles: (1)a two-stroke air motor sub-cycle and (2) a two-stroke combustion enginesub-cycle, wherein the two types of power strokes are executed onalternating rotations of the crankshaft 136 and the “exhaust” from theair power stroke becomes the “intake” for the internal combustionprocess. With an exhaust valve of the cylinder 156 closed, a charge ofisothermally compressed air from the capacitance tanks 104 is injectedinto a cylinder 156 of the combustion engine 106 when the piston 160 ofthe associated cylinder 156 is at or near TDC at the beginning of theair motor power stroke. In some embodiments, the injection of compressedair into a cylinder 156 may begin when the associated piston 160 ispositioned at TDC and continue until the angle of rotation of thecrankshaft 136 is about +1 degrees, about +2 degrees, about +3 degrees,about +5 degrees, about +10 degrees, about +15 degrees, and/or about +30degrees. Still further, in alternative embodiments, the injection ofcompressed air into a cylinder 156 may begin when the angle of rotationof the crankshaft 136 is between about −30 degrees, about −15 degrees,about −10 degrees, about −5 degrees, about −3 degrees, about −2 degrees,and/or about 0 degrees and continue until the angle of rotation of thecrankshaft 136 is about TDC, about +1 degrees, about +2 degrees, about+3 degrees, about +5 degrees, about +10 degrees, about +15 degrees,and/or about +30 degrees. In some embodiments, it will be appreciatedthat the timing and duration of the injection of the compressed air mayfurther be dependent on crankshaft 136 rotational speed and/or otheroperating or design parameters of the combustion engine 106.

The charge of compressed air may fill the cylinder 156 and absorb wasteheat lingering from a previous combustion event. The charge ofcompressed air may gain additional expansion as a result of absorbingthe waste heat. Accordingly, the air within the cylinder 156 may propelthe piston 160 downward. In some embodiments, the propulsion of thepiston away from the TDC position may significantly reduce and/oreliminate conventional pumping losses by substituting a compressed airpower stroke for the conventional intake event. Accordingly, theinjection of the charge of isothermally compressed air may increasepower output of the IsoC engine 100 via the scavenging of waste heatwithout injecting additional fuel into the cylinder.

In some embodiments, the charge of compressed air injected into acylinder 156 may be dependent on the static compression ratio of thecombustion engine 106. For example, a charge of compressed air having apressure of about 147 pounds per square inch (psi; about 10 bar) may beinjected at about TDC into a cylinder 156 for a combustion engine 106having a compression ratio of about 10:1. This would result in about14.7 psi of pressure within the cylinder 156 after expansion when thepiston 160 is at bottom dead center (BDC) position. Accordingly, thepressure of the charge of compressed air injected into the cylinder 156may be adjusted so that the pressure inside the cylinder 156 of thecombustion engine 106 at BDC is about 14.7 psi and/or any other pressurethat promotes proper combustion within the cylinder 156. In someembodiments, the compression stroke may begin in a cooler environment ascompared to a traditional adiabatic compression engine because theisothermal compression charge introduced at TDC has been expanded at aratio of 10:1 when the piston 160 reaches BDC, giving it a temperaturebelow that of the ambient air at the beginning of the upstroke.Additionally, the heated surfaces of the cylinder 156 may drive a moreaggressive expansion of the compressed gases during the compressed airpower stroke, scavenging this waste heat and delivering it to thecrankshaft 136 in the form of additional work. As a result of the coolerenvironment, the crankshaft 136 may experience a decreased load on theupstroke that promotes a cooler compression charge and an increasedefficiency from a combustion event that occurs when fuel is injectedinto the cylinder 156 as the piston 160 returns to the TDC position.After ignition and combustion, the power stroke and the exhaust strokeof the four-stroke IsoC engine 100 may be substantially similar to thepower stroke and the exhaust stroke of a traditional four-strokeadiabatic compression engine.

Still referring to FIG. 1, the IsoC engine 100 may be installed in avehicle and configured to propel the vehicle. It is contemplated by thisdisclosure that the IsoC engine 100 may be employed in variousapplications, including but not limited to, vehicles, heavy machinery,power plants, generator sets, combustion engine-powered tools andequipment, surface and submarine sea craft, and any other suitablecombustion engine-powered apparatus where increased fuel efficiency,decreased emissions, reduced operating temperatures and/or lessrestrictive design constraints may be beneficial.

Embodiments of both the two-stroke combustion engine configuration andthe four-stroke combustion engine configuration of the IsoC engine 100may also provide additional benefits. By coupling the compressor 102 tothe combustion engine 106 through the crankshaft 136 via a selectivelyengaged compressor clutch 130, the IsoC engine 100 is configured forregenerative braking which may further increase the efficiency of theIsoC engine 100. During deceleration of the IsoC engine 100, energy maybe transferred to the compressor 102 through the crankshaft 136 byengaging the compressor clutch 130. The compressor 102 may thus recoverenergy normally lost during deceleration and use this energy toisothermally compress additional air and replenish a supply ofcompressed air stored in the capacitance tanks 104. As a result, the“braking charge” may be used to propel a vehicle or other piece ofequipment from an idle position, further reducing fuel consumption andemissions.

The IsoC engine 100 may also comprise no idling requirement, similar tocurrent gas-electric hybrid applications. When a vehicle or otherapparatus comprising an IsoC engine 100 requires no demand for powerand/or the vehicle or apparatus remains idle, the IsoC engine 100 mayshut down completely by discontinuing the injection of compressed airfrom the capacitance tanks 104 or by selectively operating the shutoffvalve 118. Additionally, the IsoC engine 100 may also cease fueldelivery from the fuel system 140. The IsoC engine 100 may then berestarted as a compressed air motor utilizing compressed air injectiononly. Upon a demand for acceleration, the IsoC engine 100 may resumecompressed air injection into the combustion engine 106 and may furtherresume fuel injection and fuel combustion of the compressed air and fuelmixture when the fuel combustion may be performed with a maximumefficiency. The dual drive functionality of the IsoC engine 100,operating as both a combustion engine and a compressed air motor, may beselectively managed to optimize performance, efficiency and emissions.

The IsoC engine 100 may also be configured for a zero emissions mode. Insome embodiments, the IsoC engine 100 may be operated by driving thepistons 160 of the combustion engine 106 without fuel from the fuelsystem 140 and only with a charge of compressed air provided by thecapacitance tanks 104. For example, on trips of short duration and/or inheavy start-stop traffic, the IsoC engine 100 may utilize its zeroemissions air-motor mode first and resort to fuel combustion only whencombustion can be performed with a maximum efficiency. Further, athighway speeds and/or during extended cruising, fuel combustion may beselectively engaged to provide continuous power and replenish anydepleted capacity of the capacitance tanks 104.

The IsoC engine 100 may also be configured to decrease carbon emissions.The IsoC engine 100 comprises a carbon dioxide sequestration filter 120between the capacitance tanks 104 and the combustion engine 106. Thecarbon dioxide sequestration filter 120 comprises a replaceablecartridge of granulated metal oxides that may sequester carbon dioxideduring continuous duty operation. Fueling the IsoC engine 100 using atrue carbon-neutral biofuel while the pneumatic hardware is configuredto sequester free atmospheric carbon dioxide may lead to a netcarbon-negative operating cycle.

The IsoC engine 100 may also be configured for grid-powered operation.The IsoC engine 100 comprises an external fill port 116 configured tocouple to an external compressed air source to allow the at least onecapacitance tank 104 to receive compressed air through the external fillport 116 from the external compressed air source. Accordingly, thecapacitance tanks 104 may be filled using a stationary pump and/or otherfixed or mobile compressed air source.

The IsoC engine 100 may be configured to take advantage of some or allof the efficiency increasing benefits described herein. Such benefits asincreased static compression ratios, improved lean burn capacity,greater flexibility in fueling options, regenerative braking, no engineidling requirement, and a zero emissions air motor mode may beselectively employed to maximize the efficiency of a vehicle or otherapparatus having an IsoC engine 100. Accordingly, by recoveringotherwise rejected heat energy and selectively implementing fuelcombustion, the IsoC engine 100 is capable of attaining a substantialincrease in fuel efficiency over a traditional adiabatic compressionengine. In some embodiments, the IsoC engine 100 may also attain higherfuel efficiencies than traditional gas-electric hybrid vehicles. Forexample, in some embodiments, a passenger vehicle having an IsoC engine100 may attain fuel efficiencies of at least about 40 miles per gallon(mpg), at least about 50 mpg, at least about 60 mpg, at least about 70mpg, at least about 80 mpg, and/or at least about 90 mpg. Additionally,the IsoC engine 100 may be selectively configured so that its attributesare directed towards maximizing power density and power output ratherthan fuel economy, for high performance and racing purposes, and otherapplications where fuel efficiency is considered secondary to therequirement to maximize power output and performance.

Referring now to FIG. 2, a schematic diagram of an isothermalcompression based combustion (IsoC) engine 100 electronic control system200 is shown according to an embodiment of the disclosure. Electroniccontrol system 200 is electronically coupled to the IsoC engine 100 ofFIG. 1. Electronic control system 200 comprises an electronic controlunit (ECU) 202 configured to monitor operating parameters of the IsoCengine 100 through a plurality of sensor inputs 206. ECU 202 alsocomprises a plurality of control outputs 208 and is configured tocontrol the operation of the IsoC engine 100 through the plurality ofcontrol outputs 208 in response to monitoring operation of the IsoCengine 100 through the sensor inputs 206. The electronic control system200 also comprises a user interface 204 that may be configured forselectively inputting a demand for power, efficiency, acceleration,and/or reduction of acceleration from an IsoC engine 100. The userinterface 202 may comprise a pedal, a toggle switch, a throttle, atrigger, or any other adjustable means for selectively inputting ademand for power, efficiency, acceleration, and/or reduction ofacceleration in a vehicle or other apparatus comprising an IsoC engine100.

The ECU 202 may generally be configured as an Application SpecificIntegrated Circuit (ASIC) and/or comprise a general purpose processor.The ECU 202 may also be configured to be programmable and/or store oneor more fuel maps and air maps to allow the ECU 202 to control operationof the IsoC engine 100 through the control outputs 208 as a result ofmonitoring the sensor inputs 206. For example, the ECU 202 may moreheavily employ the compressed air from the capacitance tanks 204 at lowcrankshaft 136 rotational speeds and more heavily employ the fuel system140 at high crankshaft 136 rotational speeds in a manner similar totraditional hybrid gas-electric engines. Furthermore, the ECU 202 may beconfigured to manage pressures and temperatures throughout the IsoCengine 100, govern the balance between air-motor and fuel combustiondrive modes, and modify combustion mixtures as a result of one or morefuel maps stored in the ECU 202.

To implement control of the IsoC engine 100, the ECU 202 may monitor theplurality of sensors inputs 206 that may communicate information to theECU 202. Such information may include temperature and/or pressure of thecompressor 102, the combustion engine 106, the turbocharger 108, thepressure regulator 122, the air rail 124, the air injectors 126, theexhaust manifold 128, the compressor exhaust 132, the intake pipe 134,the fuel system 140, the fuel reservoir 142, the fuel pump 144, the fuelrail 148, the fuel injectors 150, the exhaust pipe 152, the catalyticconverter 154, the cylinders 156, and/or any other component of the IsoCengine 100. Additionally, the sensor inputs 206 may communicateinformation to the ECU 202 that is related to the air capacitance levelof the capacitance tanks 104, the status of the check valve 114,connection status to the external fill port 116, function of the airinjectors 126, fuel level in the fuel reservoir 142, function of thefuel injectors 150, crankshaft 136 angle, crankshaft 136 rotationalspeed, and/or any other operating and/or status parameter necessary forthe ECU 202 to exhibit control of the IsoC engine 100.

As a result of monitoring the sensor inputs 206, the ECU 202 may controlthe IsoC engine 100 through the plurality of control outputs 208. Thecontrol outputs 208 may generally comprise selectively operating thecompressor 102, dispersing compressed air from the capacitance tanks104, selectively operating the combustion engine 106, selectivelyoperating the shutoff valve 118, selectively adjusting the pressureregulator 122, selectively controlling and/or operating the airinjectors 126, selectively engaging and disengaging the compressorclutch 130, selectively operating the compressor fan 138, selectivelycontrolling and/or operating the fuel system 140, and/or selectivelycontrolling and/or operating the fuel injectors 150. The ECU 202 mayalso control the IsoC engine 100 through the plurality of controloutputs 208 as a result of a change in a demand for power, efficiency,acceleration, and/or reduction in acceleration received by the ECU 202through the user interface 204. The ECU 202 may also control the IsoCengine 100 through the control outputs 208 in accordance with preloadedfuel maps and/or air maps stored in the ECU 202. Additionally, the ECU202 may be configured to continuously vary the timing of compressed airinjection, the timing of fuel injection, and the timing of sparkignition.

Referring now to FIG. 3, a flowchart of a method 300 of operating anisothermal compression based combustion (IsoC) engine 100 is shownaccording to an embodiment of the disclosure. The method 300 may beginat block 302 by isothermally compressing air using a compressor 102. Insome embodiments, the compressor 102 may isothermally compress the airby dissipating heat through at least one heat exchanger 158. The methodmay continue at block 304 by storing the compressed air in at least onecapacitance tank 104. The method may continue at block 306 byselectively injecting a volume of isothermally compressed air into acylinder 156 of a combustion engine 106 when an associated piston 160 isat about top dead center (TDC). The method may continue at block 308 byselectively injecting a volume of fuel into the cylinder 156. Inembodiments having a two-stroke combustion engine, the volume of fuelmay be injected simultaneously with the compressed air. In embodimentshaving a four-stroke combustion engine, the volume of fuel may beinjected during the air-motor power stroke and/or the compression strokeof the four-stroke combustion engine 106. However, in some embodiments,no volume of fuel may be injected into the cylinder 156. The method mayconclude at block 310 combusting the mixture of the volume ofisothermally compressed air and the volume of fuel in the cylinder ofthe combustion engine 106. In some embodiments, combusting the mixtureof the volume of isothermally compressed air and the volume of fuel maybe initiated by selectively firing a spark plug in the cylinder 156 ofthe combustion engine 106.

Referring now to FIG. 4, a flowchart of a method 400 of controlling anisothermal compression based combustion (IsoC) engine 100 is shownaccording to an embodiment of the disclosure. The method 400 may beginat block 402 by selectively injecting a volume of isothermallycompressed air into a cylinder 156 of a combustion engine 106 when anassociated piston 160 is at about top dead center (TDC). The method maycontinue at block 404 by selectively injecting a volume of fuel into thecylinder 156. In embodiments having a two-stroke combustion engine, thevolume of fuel may be injected simultaneously with the compressed air.In embodiments having a four-stroke combustion engine, the volume offuel may be injected during the air-motor power stroke and/or thecompression stroke of the four-stroke combustion engine. However, insome embodiments, no volume of fuel may be injected into the cylinder156. The method may continue at block 406 by selectively receiving aninput through a user interface 204. The method may conclude at block 408by selectively adjusting at least one of the volume of compressed airand the volume of fuel injected into a cylinder 156 of the combustionengine 106. In some embodiments, selectively adjusting at least one ofthe volume of compressed air and the volume of fuel may be implementedby the ECU 202 communicating with and/or controlling at least onecontrol output 208. Further, in some embodiments, the ECU 202 mayimplement the selective adjustment of at least one of the volume ofcompressed air and the volume of fuel in response to communicating withat least one sensor input 206.

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc., greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R_(l), and an upperlimit, R_(u), is disclosed, any number falling within the range isspecifically disclosed. In particular, the following numbers within therange are specifically disclosed R=R_(l)+k*(R_(u)−R_(l)), wherein k is avariable ranging from 1 percent to 100 percent with a 1 percentincrement, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent,96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Unlessotherwise stated, the term “about” shall mean plus or minus 10 percentof the subsequent value. Moreover, any numerical range defined by two Rnumbers as defined above is also specifically disclosed. Use of the term“optionally” with respect to any element of a claim means that theelement is required, or alternatively, that the element is not required,both alternatives being within the scope of the claim. Use of broaderterms such as “comprises,” “includes,” and “having” should be understoodto provide support for narrower terms such as “consisting of,”“consisting essentially of,” and “comprised substantially of.”Accordingly, the scope of protection is not limited by the descriptionset out above but is defined by the claims that follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated as further disclosure into the specificationand the claims are embodiment(s) of the present invention. Thediscussion of a reference in the disclosure is not an admission that itis prior art, especially any reference that has a publication date afterthe priority date of this application. The disclosure of all patents,patent applications, and publications cited in the disclosure are herebyincorporated by reference, to the extent that they provide exemplary,procedural, or other details supplementary to the disclosure.

What is claimed is:
 1. An isothermal compression based combustion (IsoC)engine, comprising: a compressor configured to isothermally compress avolume of air; at least one capacitance tank coupled to the compressorand configured to store the volume of isothermally compressed air; and acombustion engine configured to: receive at least a portion of thevolume of isothermally compressed air from the at least one capacitancetank and into a cylinder of the combustion engine; at least one of (1)selectively inject a volume of fuel into the cylinder and ignite thevolume of fuel in the presence of the volume of air in the cylinder and(2) selectively omit the injection of a volume of fuel and expand thevolume of air in the cylinder using no combustion.
 2. The IsoC engine ofclaim 1, wherein the volume of air is received into the cylinder when anassociated piston is at about a top dead center (TDC) position.
 3. TheIsoC engine of claim 1, wherein the volume of air is received into thecylinder when an associated piston is between about a top dead center(TDC) position and about a 20 degree rotation beyond the TDC position.4. The IsoC engine of claim 1, wherein the compressor comprises amultistage, intercooled compressor and is configured to dissipate heatgenerated as a result of compressing the volume of air.
 5. The IsoCengine of claim 1, wherein the volume of compressed air received intothe cylinder comprises a temperature at about ambient temperature of thesurrounding environment.
 6. The IsoC engine of claim 1, wherein thecombustion engine is configured to substantially eliminate autoignitionof a volume of fuel selectively injected into the cylinder.
 7. The IsoCengine of claim 1, further comprising: a turbocharger driven by anexhaust stream from the combustion engine and configured to force inducean intake of the compressor.
 8. The IsoC engine of claim 1, wherein thecompressor is coupled to a crankshaft of the combustion engine through acompressor clutch, and wherein the crankshaft is configured to operatethe compressor when the compressor clutch is engaged.
 9. The IsoC engineof claim 1, wherein the combustion engine comprises a two-strokeoperating cycle comprising an exhaust stroke and a working stroke, andwherein the receiving the at least a portion of the volume ofisothermally compressed air volume from the at least one capacitancetank and into a cylinder and selective injection of the volume of fuelinto the cylinder occur substantially simultaneously.
 10. The IsoCengine of claim 1, wherein the combustion engine comprises a four-strokeoperating cycle comprising an air-motor power stroke, a compressionstroke, a combustion power stroke, and an exhaust stroke, wherein theinjection of the at least a portion of the volume of isothermallycompressed air into the cylinder occurs when an associated piston is atabout a top dead center (TDC) position at the beginning of the air-motorpower stroke, and wherein the selective injection of the volume of fueloccurs during at least one of the air-motor power stroke and thecompression stroke.
 11. A method of operating an isothermal compressionbased combustion (IsoC) engine, comprising: isothermally compressing afirst volume of air; passing the isothermally compressed volume of airto at least one capacitance tank; storing the isothermally compressedvolume of air in the at least one capacitance tank; injecting a secondvolume of isothermally compressed air into a cylinder of a combustionengine when an associated piston is at about a top dead center (TDC)position; selectively injecting a volume of fuel into the cylinder ofthe combustion engine; and combusting the mixture of the second volumeof isothermally compressed air and the volume of fuel in the cylinder ofthe combustion engine.
 12. The method of claim 11, wherein selectivelyinjecting a volume of fuel into the cylinder of the combustion engineoccurs simultaneously with the injecting a second volume of isothermallycompressed air.
 13. The method of claim 11, further comprising:selectively ceasing the injection of a volume of fuel into thecombustion cylinder; and continuing to inject the second volume ofisothermally compressed air into a cylinder of a combustion engine whenan associated piston is at about a top dead center (TDC) position tocause the combustion engine to operate.
 14. The method of claim 11,wherein the injecting the second volume of isothermally compressed airinto the cylinder of the combustion engine and the selectively injectingthe volume of fuel into the cylinder of the combustion engine occurssubstantially simultaneously.
 15. The method of claim 11, wherein theinjecting the second volume of isothermally compressed air into thecylinder of the combustion engine occurs when the associated piston isat about a top dead center (TDC) position prior to an air-motor powerstroke and the selectively injecting the volume of fuel into thecylinder of the combustion engine occurs during at least one of theair-motor power stroke and the compression stroke.
 16. A method ofcontrolling an isothermal compression based combustion (IsoC) engine,comprising: selectively injecting a volume of isothermally compressedair into a cylinder of a combustion engine when an associated piston isat about a top dead center (TDC) position; selectively injecting avolume of fuel into the cylinder; selectively receiving an input througha user interface; and selectively adjusting at least one of the volumeof compressed air and the volume of fuel injected into a cylinder of thecombustion engine during subsequent rotations of a crankshaft of thecombustion engine.
 17. The method of claim 16, wherein the selectivelyadjusting at least one of the volume of compressed air and the volume offuel injected into the cylinder may be implemented by an electroniccontrol unit (ECU) in response to monitoring at least one sensor input.18. The method of claim 17, wherein the selectively adjusting at leastone of the volume of compressed air and the volume of fuel injected intothe cylinder may be implemented by the ECU communicating with at leastone control output.
 19. The method of claim 18, wherein the selectivelyadjusting at least one of the volume of compressed air and the volume offuel injected into the cylinder may be implemented by the ECU inresponse to an input received through the user interface.
 20. The methodof claim 19, wherein the ECU is configured to selectively control theIsoC engine in accordance with at least one of a preloaded fuel mapstored in the ECU and a preloaded air map stored in the ECU.